Kernel: Add a syscall to clear the profiling buffer

While profiling all processes the profile buffer lives forever. Once you have copied the profile to disk, there's no need to keep it in memory. This syscall surfaces the ability to clear that buffer.
AmusedNetwork · Apr 19, 2021 · 4ed682a · 4ed682a
1 parent cdd9faa
commit 4ed682a
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Showing 4 changed files with 42 additions and 0 deletions.
diff --git a/Kernel/API/Syscall.h b/Kernel/API/Syscall.h
@@ -171,6 +171,7 @@ namespace Kernel {
  S(purge) \
  S(profiling_enable) \
  S(profiling_disable) \
+ S(profiling_free_buffer) \
  S(futex) \
  S(chroot) \
  S(pledge) \

diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
@@ -700,6 +700,12 @@ bool Process::create_perf_events_buffer_if_needed()
  return !!m_perf_event_buffer;
 }
 
+void Process::delete_perf_events_buffer()
+{
+ if (m_perf_event_buffer)
+ m_perf_event_buffer = nullptr;
+}
+
 bool Process::remove_thread(Thread& thread)
 {
  ProtectedDataMutationScope scope { *this };

diff --git a/Kernel/Process.h b/Kernel/Process.h
@@ -394,6 +394,7 @@ class Process
  KResultOr<int> sys$module_unload(Userspace<const char*> name, size_t name_length);
  KResultOr<int> sys$profiling_enable(pid_t);
  KResultOr<int> sys$profiling_disable(pid_t);
+ KResultOr<int> sys$profiling_free_buffer(pid_t);
  KResultOr<int> sys$futex(Userspace<const Syscall::SC_futex_params*>);
  KResultOr<int> sys$chroot(Userspace<const char*> path, size_t path_length, int mount_flags);
  KResultOr<int> sys$pledge(Userspace<const Syscall::SC_pledge_params*>);
@@ -520,6 +521,7 @@ class Process
  bool dump_core();
  bool dump_perfcore();
  bool create_perf_events_buffer_if_needed();
+ void delete_perf_events_buffer();
 
  KResult do_exec(NonnullRefPtr<FileDescription> main_program_description, Vector<String> arguments, Vector<String> environment, RefPtr<FileDescription> interpreter_description, Thread*& new_main_thread, u32& prev_flags, const Elf32_Ehdr& main_program_header);
  KResultOr<ssize_t> do_write(FileDescription&, const UserOrKernelBuffer&, size_t);

diff --git a/Kernel/Syscalls/profiling.cpp b/Kernel/Syscalls/profiling.cpp
@@ -67,6 +67,8 @@ KResultOr<int> Process::sys$profiling_enable(pid_t pid)
 
 KResultOr<int> Process::sys$profiling_disable(pid_t pid)
 {
+ REQUIRE_NO_PROMISES;
+
  if (pid == -1) {
  if (!is_superuser())
  return EPERM;
@@ -87,4 +89,35 @@ KResultOr<int> Process::sys$profiling_disable(pid_t pid)
  return 0;
 }
 
+KResultOr<int> Process::sys$profiling_free_buffer(pid_t pid)
+{
+ REQUIRE_NO_PROMISES;
+
+ if (pid == -1) {
+ if (!is_superuser())
+ return EPERM;
+
+ OwnPtr<PerformanceEventBuffer> perf_events;
+
+ {
+ ScopedCritical critical;
+
+ perf_events = g_global_perf_events;
+ g_global_perf_events = nullptr;
+ }
+
+ return 0;
+ }
+
+ ScopedSpinLock lock(g_processes_lock);
+ auto process = Process::from_pid(pid);
+ if (!process)
+ return ESRCH;
+ if (!is_superuser() && process->uid() != euid())
+ return EPERM;
+ if (process->is_profiling())
+ return EINVAL;
+ process->delete_perf_events_buffer();
+ return 0;
+}
 }